Metallicities & Activities of Southern Stars

TL;DR

This study measures metallicities and chromospheric activities of 353 bright southern stars using high-resolution spectroscopy, revealing a bimodal activity distribution and estimating the Maunder Minimum phase occurrence.

Contribution

It provides a new high-resolution spectroscopic dataset of southern stars' metallicities and activities, with a custom fitting method and analysis of Maunder Minimum status.

Findings

Metallicity measurements agree with previous determinations within 0.05-0.1 dex.

Chromospheric activity distribution is bimodal.

Approximately 6% of stars may be in Maunder Minimum phase.

Abstract

We present the results from high-resolution spectroscopic measurements to determine metallicities and activities of bright stars in the southern hemisphere. We have measured the iron abundances ([Fe/H]) and chromospheric emission indices (logR'HK) of 353 solar-type stars with V=7.5-9.5. [Fe/H] abundances are determined using a custom chi^2 fitting procedure within a large grid of Kurucz model atmospheres. The chromospheric activities were determined by measuring the amount of emission in the cores of the strong CaII HK lines. The sample of metallicities has been compared to other [Fe/H] determinations and was found to agree with these at the +/-0.05 dex level for spectroscopic values and at the +/-0.1 dex level for photometric values. The distribution of chromospheric activities is found to be described by a bimodal distribution, agreeing well with the conclusions from other works. Also an analysis of Maunder Minimum status was attempted and it was found that 6+/-4 stars in the sample could be in a Maunder Minimum phase of their evolution and hence the Sun should only spend a few per cent of its main sequence lifetime in Maunder Minimum.